The above-mentioned works mainly focused on abstract time-evolution operators.
To realize such operators in practice, especially the collective controls, various theoretical models have been considered [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}.
For instances, the spin-chain battery uses an intrinsic spin-spin interaction to realize the collective controls [10]} while the Dicke battery relies on the cavity photons to generate an effective interaction among its battery cells [1]}, [18]}.
Based on superconducting qubits, a quantum battery has just recently been realized in experiment [24]}.
